1. Field of the Invention
This invention pertains in general to the field of gemstone cutting and in particular to an apparatus and method for cone shaping the crown and pavilion portion of gemstones, especially diamonds, prior to facet polishing for use in jewelry.
2. Description of the Prior Art
Gemstones are minerals or petrified substances, such as diamonds or turquoise, that can be cut and polished for placement in jewelry. The most famous and precious gemstone is the diamond, which is a colorless mineral composed entirely of carbon crystallized in the isometric system as octahedrons, dodecahedrons, and cubes. Although this invention encompasses gemstones in general, for purposes of discussion hereinafter, reference is made primarily to the diamond as the diamond is the hardest substance and often most valued by modern society. The diamond epitomizes the cost saving inventive method of this invention, because the transition from a rough stone to brilliant cut requires time consuming, costly, highly skilled laborers. A second factor is the costly wear and maintenance of expensive faceting equipment and diamond impregnated grinding wheels. The reason why diamond cutting is an extremely laborious task and expensive process compared to other gemstones is that other than the diamond being the hardest substance, it also has grain and knots similar to wood with regard to the grain or knots, so must the diamond cutter orient the diamond before it comes in contact with the grinding wheel, and if he does encounter a twisted grain or knot ( which is almost always invisible, even to the trained eye), he can occasionally take days to grind one facet (face).
The majority of rough carbon stones used to produce brilliant cut diamonds have an irregular octahedron configuration which approximates the shape of an irregular four-sided pyramid joined at its base to another irregular four-sided pyramid. The rough stones are individually studied by the skilled laborer to determine whether one or two finished gem quality diamonds (for jewelry) are to be made from the stone. The main determination of cutting a rough stone depends upon whether the cut will result in maximum weight retention. Generally, the conversion of a rough stone diamond to a finished diamond results in the loss of approximately fifty percent of the original stone weight. Thus, two major disadvantages to the prior art is the costly need for skilled laborers to spend an excessive amount of time grinding away the unwanted bulk together with the fact that approximately 90% of the weight loss during conversion is not salvageable.
The first step in diamond cutting consists of sawing the rough stone essentially parallel to the major axis of the octahedron by a very thin phosphorous bronze disk blade having a thickness of approximately two to three one-thousandths of an inch. The edge of a blade is coated with a paste of olive oil and diamond powder.
If two diamonds are to be made from a single rough stone, each of the sawed halves are thereafter individually processed by first girdling,(brutting) or creating a cylindrical surface around the outer circumference of the stone. The girdling (brutting) is accomplished by cementing one sawed diamond half to a dop and then fixing the dop within a lathe type machine such that it rotates about an axial center line of the girdled diameter. During rotation, a technician hand machines the girdle around the stone by using an industrial diamond attached to the head of a relatively long stick. Another method to girdle (brutt) the rough diamond and other gemstones is to move a rotating dop having the rough stone centered therein into contact with a rotating grinding wheel.
Once the rough diamond has been girdled, the main reference configuration has been prepared from which all other operations comprising cutting and polishing of the stone are referenced with regard thereto. Namely, the crown (top) and pavilion (bottom) portions of the diamonds are cut and polished into a conical shape. It should be noted that the shaping/coning of the top/crown is shaped at 34.degree. and the bottom pavilion at 41 for diamonds. These angles are the same used in the faceting process. These angles are unique to diamonds providing the completed diamond with optimum brilliance. These angles will vary from one gemstone material to another. Each facet on the finished diamond is individually cut and polished by hand. Facets are placed on the crown and pavilion by use of a large rotating cast iron wheel impregnated with diamond powder. The diamond is held in the dop attached to a tang. The dop is held in a fixed position and pressed against the wheel as it rotates. A new position is set for each facet to be grounded. The skilled technician proceeds to grind and polish each of the facets onto the surface of the stone to a predetermined depth. It should be noted that the diamond can only be ground in accordance with its crystalline structure. Further, throughout the above mentioned steps, diamond or diamond powder is required. Course Diamond powder is used for the rough cutting of the facets, and fine diamond powder for the polishing of the facets.
U.S. Pat. No. 3,202,147 issued to Roos discloses a method for making the girdle using a first axially aligned motor and dop having a diamond attached thereto angled at 90.degree. to another axially aligned motor and dop having a second diamond attached thereto. Roos allows for bringing the rotating rough diamonds into contact with each other such that the axis of rotation of each crosses each other and whereby each of the rotating rough diamond chips the other and forms a hollow girdle on each. By moving the rotating dops backward and forward in an axial direction, girdles having purely straight profiles are obtained. When the operator sees that one stone has the correct sized girdle, it is replaced by a new rough stone and the process is continued until the other stone has assumed the correct size and shape and so on. Roos fails to disclose or teach a method to cone the crown or the pavilion portions of the stone.
Accordingly, the instant invention overcomes the above mentioned shortcoming by providing a method and apparatus which reduces the overall cutting time from rough stone to a facet-ready stone and teaches reducing the need for a skilled technician or diamond cutter by precisely shaping the crown and pavilion portions of the rough stone into a preform shape ready for placement of facets. The preformed diamond is now within ten percent of its final polished weight. Time saving is further realized with the invention through a process and a machine that permits diamond coning of at least two diamonds simultaneously without the need of grinding wheels thus permitting capture of nearly 100% of produced diamond dust.
The difficulty overcome by my invention is that in prior art the removal of unwanted bulk from gemstones was accomplished using costly highly skilled craftsman with expensive high maintenance machines whereas my invention efficiently and accurately removes the unwanted bulk and retains it using a relatively low cost machine with low cost maintenance and very low skilled workers and at least twice the speed of removal by prior art.
Precision cone making as described herein by any means is a novel unique process that has not been done before in precious gemstone cutting. The invention may also be used to shape synthetic and industrial diamonds for industrial gem purposes.